1. Field of the Invention
The present invention relates to a main-shaft lubricant oil supply device for adjusting the amount of to-be-supplied lubricant oil to an optimum amount, by detecting the amount of collected lubricant oil.
2. Description of the Related Art
For example, a machining tool is rotatably supported at its main shaft by a plurality of rolling bearings. Generally, a bearing is constituted by an inner ring, an outer ring, a plurality of rolling members and a holding device for holding the rolling members at equal intervals, wherein the rolling members are movably incorporated therein. The inner ring is press-fitted to the main shaft and is rotated together with the main shaft, and the outer ring is incorporated in a housing and is secured by being pressed in the axial direction by a pressing lid. Lubricant oil is filled in or supplied to the bearing, and an oil film is formed between the inner ring and outer ring and the rolling members during the rotation of the main shaft. As methods for lubricating bearings, there have been known a grease lubrication method, an oil-air lubrication method, an oil mist lubrication method, a jet lubrication method and the like. In the respective lubrication methods, the amount of lubricant oil supplied to the bearing is determined by the lubricant oil contained in the grease filled in the bearing, in the case of the grease lubrication method. In the case of the oil-air lubrication method, oil mist lubrication method and jet lubrication method, the amount of lubricant oil supplied to the bearing is determined by the amount of lubricant oil supplied from a lubricant oil supply device per set time period. In order to rotate the main shaft with high accuracy, there is a need for forming a uniform oil film, and therefore, it is required that the amount of lubricant oil supplied to the bearing be adjusted to an optimum amount. In this case, it is difficult to adjust the amount of lubricant oil with the grease lubrication method. Further, it is necessary to check if the lubricant oil has been uniformly supplied through lubricant oil supply paths, in the oil-air lubrication method, oil mist lubrication method and jet lubrication method.
In order to improve the aforementioned situations, there has been known a device for detecting abnormalities by using a device employing an optical sensor along the path between the lubricant oil supply device and the bearing (refer to Japanese Unexamined Patent Application Publication No. 2002-126909 and Japanese Unexamined Utility Model Application Publication No. 3-99300, for example).
With such a conventional device, it is possible to check the amount of lubricant oil supplied to the bearing, but it is difficult to check the amount of lubricant oil which actually exists around the rolling surface of the bearing and the rolling members and relates to lubrication, after the lubricant oil is supplied. This may result in a superfluity or shortage of lubricant oil, thereby destabilizing the oil film. This may make it difficult to rotate the main shaft with high accuracy and, in the worst case, may produce abnormal heat, thereby damaging the bearing.
Further, there has been known a main-shaft device including a device for controlling the amount of lubricant oil supplied to a bearing portion as described above, according to the rise in temperature of the lubricant oil collected from the bearing portion (refer to Japanese Unexamined Patent Application Publication No. 11-166549, for example).
With this conventional device, it is difficult to determine whether the temperature rise is caused by the shortage of lubricant oil or the superfluity of lubricant oil and also whether the temperature rise is caused by an influence of a motor in the case where the main shaft includes the motor near the bearing.